code: def nonzero(self):
      # CSC can't use _cs_matrix's .nonzero method because it
      # returns the indices sorted for self transposed.
  
      # Get row and col indices, from _cs_matrix.tocoo
      major_dim, minor_dim = self._swap(self.shape)
      minor_indices = self.indices
      major_indices = np.empty(
          len(minor_indices), dtype=self.indices.dtype
      )
      expandptr(major_dim, self.indptr, major_indices)
      row, col = self._swap((major_indices, minor_indices))
  
      # Remove explicit zeros
      nz_mask = self.data != 0
      row = row[nz_mask]
      col = col[nz_mask]
  
      # Sort them to be in C-style order
      ind = np.argsort(row, kind="mergesort")
      row = row[ind]
      col = col[ind]
  
      return row, col
  
imports: import numpy
  from ._matrix import spmatrix
  from ._base import _spbase, sparray
  from ._sparsetools import csc_tocsr, expandptr
  from ._sputils import upcast
  from ._compressed import _cs_matrix
label_desc: Use image node_id 5 for calling the _csc_base obj's underlying member method code with example usage: obj.nonzero() and returns: row,  col